Orthodontic onlay and method for exerting corrective traction on an impacted tooth

ABSTRACT

An orthodontic onlay which is cemented directly to an impacted tooth to aid in exerting corrective traction thereon. A curved base surface has a curvature substantially the same as an incisal portion of the tooth involved. The onlay has a series of openings or recesses leading from that surface toward the opposite surface for receiving and holding cement, thereby increasing the bond between the tooth and the onlay when the cement is applied. Bonding strength is increased further by plasma processing the surface, especially when the onlay is made from plastic. On its opposite surface the onlay has means for attaching a ligature.

United States Patent Northcutt Sept. 17, 1974 [76] Inventor: Michael E.Northcutt, 12720 Dianne Dr., Los Altos Hills, Calif. 94021 [22] Filed:May 8, 1972 [21] Appl. No.: 250,959

[52] US. Cl. 32/14 E, 32/61 [51] Int. Cl. A6lc 3/10 [58] Field of Search32/14 E, 14 A, 17, 61, 32/71 I [56] References Cited UNITED STATESPATENTS 2,239,960 4/1941 Harbart 32/17 2,756,504 7/1956 Levine l l 32/712,971,258 2/1961 Bien 32/14 A 3,250,003 5/1966 Collito 32/14 A 3,468,0319/1969 Muman 32/61 Primary Examiner-Antonio F. Guida AssistantExaminer-J. Q. Lever [57] ABSTRACT An orthodontic onlay which iscemented directly to an impacted tooth to aid in exerting correctivetraction thereon. A curved base surface has a curvature substantiallythe same as an incisal portion of the tooth involved. The onlay has aseries of openings or recesses leading from that surface toward theopposite surface for receiving and holding cement, thereby increasingthe bond between the tooth and the onlay when the cement is applied.Bonding strength is increased further by plasma processing the surface,especially when the onlay is made from plastic. On its opposite surfacethe onlay has means for attaching a ligature.

17 Claims, 12 Drawing Figures PAIENIED SEPI 1 I974 SHEET 2 BF 2ORTHODONTIC ONLAY AND METHOD FOR EXERTING CORRECTIVE TRACTION ON ANIMPACTED TOOTH BACKGROUND OF THE INVENTION Sometimes teeth fail toerupt. The problem is especially common with upper cuspid teeth, and inmany patients these fail to erupt. Currently, such teeth are completelyexposed surgically and then brought down into place by traction. Thisoperation involves the loss of much supporting bone, as well as tissue.The traction on the exposed tooth is achieved with a chain that is tiedaround the neck of the tooth, and pressure is applied to the chain topull the tooth into position. Frequently the chain has come loose andfor that reason, and sometimes others, secondary surgery has beenrequired. Even following surgery, bony defects have often remained thathave never been corrected.

BRIEF SUMMARY OF THE INVENTION The invention comprises a specializedorthodontic onlay, preferably made of plastic, and secured by cement(such as a suitable epoxy cement) directly to the tooth. By use of thisinvention it is no longer necessary to remove bone from the entirecrown. Instead, a small window incision is sufficient to gain access andto enable the desired traction.

In the use of brackets applied to teeth for other purposes, it hasheretofore been difficult to gain sufficient adhesion to enable thesesmall articles to transmit a substantial amount of traction, but in thisinvention the plastic onlay is applied by cement with the aid of aspecial plasma-processed surface and a series of openings from thesurface to be cemented, which may lead through the base of the bracket,or partway through it, and which hold additional cement and therebyenable a strong bonding force to be applied. The base surface that is tobe applied to the tooth is shaped to a curvature substantially the sameas the portion of the tooth to which it is to be adhered, and on theopposite surface is provided means for attaching a ligature.

The present invention results in tremendous saving of surgical trauma,and also greatly reduces the amount of bone and tissue that are removed.The onlay need be placed on only about one-third of the cuspid crown.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: FIG. 1 is a view infront elevation of an onlay embodying the principles of the inventionsecured to the lower portion of a cuspid tooth. The drawing is greatlyenlarged.

FIG. 2 is a view taken along the line 2-2 in FIG. 1.

FIG. 3 is a view in section taken along the line 3-3 in FIG. 2.

FIG. 4 is a view in front elevation illustrating the prior art, showingan upper row of teeth with an impacted cuspid to which a chain has beentied, after removal of a considerable amount of bone and tissue.

FIG. 5 is a view in bottom plan of the same prior art situation.

FIG. 6 is a view similar to FIG. 4 showing the application of thepresent invention, where only a small amount of tissue and bone areremoved, and onlay of this invention set in place, and a ligaturesecured thereto.

FIG. 7 is a view similar to FIG. 5 showing the application of thepresent invention.

FIG. 8 is a view similar to FIG. 6 illustrating the position somewhatlater, after the application of the ligature has helped the tooth erupt.At this point, the onlay may be removed and the eruption continued to beassisted by braces until the tooth reaches a substantially normalposition.

FIG. 9 is a view similar to FIG. 3 showing a modified form of theinvention applied to the rear surface of a cuspid.

FIG. 10 is a view similar to FIG. 9 showing another modified form of theinvention wherein the onlay encloses the whole lowermost portion of thecuspid on all surfaces.

FIG. 11 is a further enlarged view of a modified form of onlay havingrecesses instead of through openings in order to secure improved cementbonding, as compared with a smooth surface.

FIG. 12 is an error curve indicating distribution of tooth shapes.

DETAILED DESCRIPTION OF THE INVENTION The invention comprises an onlay15 preferably made from plastic approximately the color of the tooth,and shaped to provide a base surface 16 that is adapted to face thesurface of a tooth 17 and an opposite surface 18 which faces outwardly.As illustrated, the tooth 17 is a cuspid or incisor, which is thecommonest tooth to have the problem, and where the most severe problemshave been confronted. The plastic may be methyl methacrylate or othersuitable material.

The onlay 15 is shaped to conform to the shape of the incisal third ofthe tooth 17 to which it is to be applied.

Thus, as shown in FIG. 3, the onlay 15 is curved from top to bottom andas shown in FIG. 2, it is also curved from side to side, to conform tothe double curve of the tooth 17. The size and shape of the onlay 15 areimportant, for it should conform very closely to the size and shape ofthe tooth 17 to which it is applied. Fortunately, as shown in FIG. 12, adistribution curve 19 of teeth size follows the familiar error curve,with ninetenths of the teeth being located between the two verticaldivisions A and B, indicating that a single size of tooth onlay 15 madeto a proper shape will fit the teeth of nine-tenths of all people. Forapproximately onetenth of them, the onlay 15 would be either too curvedor not curved enough, but this can be corrected by use of a dental burrby the orthodontist or surgeon.

The shape of the onlay 15 having been determined, an important featureof the invention is its provision of means for enhancing adhesion. Forone thing, the surface 16 may be plasma treated to give a surfaceportion 20 which enhances adhesion several times. The treatment may bedone in a chamber or reactor operating at a few torr of pressure of asuitable circulating plasma gas, such as air, oxygen, nitrogen, orhelium, with radio frequency energy applied. Oxygen or air is especiallyeffective as a plasma gas to remove films of grease or oil or otherorganic residue, with the resulting oxidation products, such as carbondioxide and water being removed. This may be followed by a helium plasmatreatment, which is followed by a purge gas. For further information,reference is made to an article entitled How to Obtain Strong AdhesiveBonds via Plasma Treatment by Richard L. Bersin in Adhesives Age forMar. 1972. Such treatment can increase the bond strength of plastics inthe order of ten times what it would be otherwise.

Furthermore, the onlay may be pierced by through 5 openings 21 (FIGS. 1and 3) or by blind openings or recesses 22 (FIG. 11) and either of thesemay be either round, square, or any other shape, extending from the basesurface 16 of the onlay 15. These openings 21 and 22 aid in theretention of cement 23 and to assist in obtaining a strong bonding forcebetween the onlay and the tooth 17. The openings 21 and 22 alwayscommunicate with the base side 16 of the onlay 15, whether they go allthe way through or not. This is an important feature of the inventionand it applies to other kinds of onlays 15 that are to be cemented to atooth. It applies, for example, to onlays used in connection with toothstraightening for retaining arch wires.

On the front side 18 of the onlay 15, the side which is opposite to thebase surface 16, a suitable means for attachment of a ligature isprovided. This may be a plastic loop 25 integral with the onlay 15, orit may comprise a metal member 26 (see FIG. 11) with two members 27going through the onlay 15, each having a grommet 28 or washer on theiropposite side, or formed otherwise into such a shape that they cannot bewithdrawn by application of strong pull.

FIG. 4 illustrates what the prior art did, and shows some of its badfeatures. The entire tooth 17 was exposed, or substantially the entiretooth, and this meant cutting away a substantial amount of tissue andbone 30, making the large hole 31. The bone in particular would almostnever regrow, and sometimes adjacent teeth were considerably weakened.

FIG. 6 illustrates in contrast how the present invention works. A verysmall window 32 is cut through the tissue and bone and then, once asmall portion of the tooth 17 has been exposed, the onlay 15 is cementedto it and a ligature 33 affixed thereto and tied to an arch wire 34. AsFIG. 8 shows, the traction exerted through the ligature 33 and arch wire34 eventually helps the tooth 17 work its way down, and eventually itnot only erupts, as shown in FIG. 8, but can be urged to its normalposition by conventional braces. or bands and brackets with an archwire.

Sometimes (see FIGS. 7 and 9) it is more convenient to secure a modifiedform of onlay 35 to the back surface of the tooth 17. Such an onlay 35has a different shape as shown in FIG. 9, but again it is a standardshape for almost all teeth. Otherwise structure and adhesion are thesame, and again there is an anchor ring 36, only on the lingual side ofthe tooth 17 instead of on the labial side.

Sometimes a cap-shaped onlay (FIG. 10) is the most convenient. Here, asmaller lower portion of the tooth 17 may be used, but both surfaces arecovered, as well as the bottom edge, and the onlay 40 has a lin' gualside 41 and a labial side 42 with respective rings or anchors 43 and 44.Usually only one of these will be used, and the other one will be cutoff by the orthodontist. Except for shape, the basic structure is thesame.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

I claim:

1. An orthodontic onlay adapted to be cemented to an impacted tooth toaid in exerting corrective traction thereon, comprising a curved basesurface having a curvature essentially the same as that of a lowerportion of such a tooth and having a lower edge of a configuration thatconforms essentially to the profile of the lower edge of the tooth,

a series of openings leading from said surface toward the oppositesurface. for receiving and holding cement and thereby increasing thebond between the tooth and the onlay when cement is placed thereon andanchor means consisting of a single closed loop on said opposite surfacefor attaching a ligature thereto, whereby the anchor means may beattached to an exposed portion of an impacted tooth, a ligature may beattached to said loop and corrective forces applied to the impactedtooth.

2. The onlay of claim 1 wherein said base surface corresponds in shapeand size to the lower front surface of the tooth.

3. The onlay of claim 1 wherein said base surface corresponds in shapeand size to the lower rear surface of the tooth.

4. The onlay of claim 1 which is cap shaped and is shaped and sized toinclose both front, rear, and bottom edge surfaces of the tooth.

5. The onlay of claim 1 wherein said anchor means comprises an integralplastic ring.

6. The onlay of claim 1 wherein said anchor means comprises a separatemetal member held to said onlay by grommets.

7. The onlay of claim 1 wherein said onlay is plastic and issubstantially the color of the tooth.

8. The onlay of claim 7 wherein said base surface is a surface that hasbeen plasma treated to enhance adhesion.

9. The onlay of claim 1 wherein said openings go all the way through thebracket.

10. The onlay of claim 1 wherein said openings extend only part waythrough the bracket.

11. The process of exerting corrective traction on an impacted toothcomprising a. exposing a small area of the lower portion of saidimpacted tooth;

b. cementing to said exposed portion an orthodontic onlay having a basesurface with openings leading from said surface toward the oppositesurface and anchor means on said opposite surface for attaching aligature thereto; and

c. attaching a ligature to said anchor means and applying tension tosaid ligature whereby said im pacted tooth is caused to move toward anerupted position.

12. The process of claim 11 wherein said onlay is made fromtooth-colored plastic.

13. The process of claim 12 wherein said onlay base surface is a plasmapretreated surface.

14. The process of claim 12 wherein said anchor means is integral withthe onlay plastic.

15. The process of claim 12 wherein said anchor means is metal securedto the plastic.

16. The process of claim 11 wherein said onlay openings go all the waythrough the onlay.

17. The process of claim 11 wherein said onlay openings are blindrecesses.

1. An orthodontic onlay adapted to be cemented to an impacted tooth toaid in exerting corrective traction thereon, comprising a curved basesurface having a curvature essentially the same as that of a lowerportion of such a tooth and having a lower edge of a configuration thatconforms essentially to the profile of the lower edge of the tooth, aseries of openings leading from said surface toward the oppositesurface, for receiving and holding cement and thereby increasing thebond between the tooth and the onlay when cement is placed thereon andanchor means consisting of a single closed loop on said opposite surfacefor attaching a ligature thereto, whereby the anchor means may beattached to an exposed portion of an impacted tooth, a ligature may beattached to said loop and corrective forces applied to the impactedtooth.
 2. The onlay of claim 1 wherein said base surface corresponds inshape and size to the lower front surface of The tooth.
 3. The onlay ofclaim 1 wherein said base surface corresponds in shape and size to thelower rear surface of the tooth.
 4. The onlay of claim 1 which is capshaped and is shaped and sized to inclose both front, rear, and bottomedge surfaces of the tooth.
 5. The onlay of claim 1 wherein said anchormeans comprises an integral plastic ring.
 6. The onlay of claim 1wherein said anchor means comprises a separate metal member held to saidonlay by grommets.
 7. The onlay of claim 1 wherein said onlay is plasticand is substantially the color of the tooth.
 8. The onlay of claim 7wherein said base surface is a surface that has been plasma treated toenhance adhesion.
 9. The onlay of claim 1 wherein said openings go allthe way through the bracket.
 10. The onlay of claim 1 wherein saidopenings extend only part way through the bracket.
 11. The process ofexerting corrective traction on an impacted tooth comprising a. exposinga small area of the lower portion of said impacted tooth; b. cementingto said exposed portion an orthodontic onlay having a base surface withopenings leading from said surface toward the opposite surface andanchor means on said opposite surface for attaching a ligature thereto;and c. attaching a ligature to said anchor means and applying tension tosaid ligature whereby said impacted tooth is caused to move toward anerupted position.
 12. The process of claim 11 wherein said onlay is madefrom tooth-colored plastic.
 13. The process of claim 12 wherein saidonlay base surface is a plasma pretreated surface.
 14. The process ofclaim 12 wherein said anchor means is integral with the onlay plastic.15. The process of claim 12 wherein said anchor means is metal securedto the plastic.
 16. The process of claim 11 wherein said onlay openingsgo all the way through the onlay.
 17. The process of claim 11 whereinsaid onlay openings are blind recesses.